Luminous tube



. anism embodying the invention, such dis-' I supported by lead-in wires 4 which conduct the necessary current tothe electrodes, each Patented June 9, 1931 I UNITED. STATES- PATENT OFFICE i HAROLD W. HOWARD, OE CLEVELAND, OHIO, ASSIGNOR TO NEON PROCESS, IN'GOR- PORATZEJ), OF. CLEVELAND,.OHIO, CORPORATION OF OHIO LUMINOUS 'runn Application filed March 16, 1929. Serial No. 347,508.

provide an electrode assembly for use in such neon and like luminous tubes which will make it possible to employ an electrode of relatively small surface area as well as one whlch will be lasting in service and-not subject to any detrimental changes in its character.

To the accomplishment of the foregoing andvrelated ends, the invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description settin forth in detail certain mech-' closed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

lln said annexed drawings Fig. 1 illustrates a typical neon or like luminous tube inwhich the present improved electrode assembly is incorporated; Fig. 2 is a sectional view, on a larger scale, of one end of such tube and the corresponding electrode assembly; Fig. 3 is a similar sectional View, but on a still larger scale, of the electrode by itself; and Fig. 4 is a view corresponding to Fig. 3, but showing a modified form of the electrode.

Referring to the structural features of the tube, the body 1 thereof is shown in the several figures of the drawings in conventional form, it being understood that such body will be of suitable diameter and length'and will ordinarily be bent in the outline of a letter orornamental design where the tube is used for advertising purposes. The ends 2 of the tube are, as shown, referably of largerdiameter than such be y 1 so as to form chambers for the corresponding electrode assemblies 3. The latter are connected with and such wire being sealed vacuum tight at the inwardly directed neck 5 where it passes throu h the end of the electrode chamber 2, and t e circuit 6, wherewith said lead-in wires are thus connected, also including the high tension secondary of a suitable transformer 7.

Referring more particularly to the electrode assembly as illustrated in the sectional vlews of Figs. 2 and 3, the electrode 8 proper consists of a short cylindrical piece of metal, ordinarilyiron, to the inner end of which the corresppnding end of the lead-in wire 4 is firmly razed or welded. Surrounding such electrode is a sheath 9 of general cup shape, the closed end of the sheath. being mounted on and secured to the end ofthe inwardly directed neck 5 throu h which the lead-in wire passes, as explains above. The sheath 9 maybe made of any suitable dielectric material. For example, it may be made-of glass, in which event it will constitute in eflect an extension of the neck to which it is attached, but preferably a more refractory dielectric material will be used. Thus a preferred material is that known as lava, through its use in the manufacture of gas tips and burners, particularly where properly prepared by glazing the surface, inside and out, with a fused coating 10 of an alkali metal silicate or such a silicate mixed with a borate or fluoride, or both, such mixtures yielding aboro-silicate or fluo-silicate.

Independently of the particular dielectric material thus used, attention is directed to the shape of the inner surface of the sheath, this surface being designed to take advantage of the fact that spraying or sputttering of the electrode material is always in a line normal to the surface from which such spraying or sputtering takes place. Thus such surface, in the first place is of a contour such that only particles that are sputtered off at right angles to the end of-the metal electrode 8 directly towards the'opposite electrode can escape from such sheath. In the second place the shape of the surface in question is such that particles that are subsequently sputtered from any point on such surface itself, where they have initially lodged, will again be deposited at some other point inside of tall in the tube tend to be absorbed action i carried too far mi the sheath and practically none will be deposited outside of the latter,',as for example, on the adjacent side walls of the tube 1 or its enlarged end 2.

To accomplish the foregoing result, in the form illustrated-in Figs. 2 and 3 the inner surface of the sheath is made of substantially conical form with the apex at the oint where the metal electrode 8 projects t erethrough. The outer, larger. end of the sheath is partiallyclosed by an inwardly directed circumferentially extendin flan e 11, the inner face of which is beve ed. a result of the surface conformation-just described, the metal particles sprayedfrom the electrode 8 are substantiall all collected, and form in the course of a s ort period of operation a coatin on the inner surface of the sheath. In ot er words, the projecting electrode Swill disappear and e replaced by such metal deposit or coating 12 that now constitutes in effect the electrode.

In the-modified construction of electrode shown in Fig. 4, the flange 11 is beveled at a somewhat more acute angle to the conical inner surface of the sheath andin addition the opening remainin at the center of such flange has a beveled e go 13. Theangularly related surfaces thus provided are adapted not only to retain the s uttered electrode material within the sheet but cause the deposit or coatin uni orm thickness. oreover, the area of the electrode thus formed by the de osit of metal on the inner wall or surface 0 the sheath will be defined by the area of such surface and any desired limit ma accordingly be im osed without danger 0 its being exceeded. here is a distinct advantage in such limitation of electrode area, for the reason that the gases withposited coating, and whileflspch a sorption is desirable u to a certain point, i. e. the elimination o so-called impurities admixed with the conductin gas as to which impurities 'a' referentia absorpltion occurs, this reduce thevapor pressure of the conducting gas itself to a value belowthat required for proper opertfii ad 1 1'1 f er m es 0 app ymg t e prmc p e10 my invention may be employed instead of the one explained, chan being made as regards themechanism herem disclosedi provided the means stated by any of the 0 owing claims or the equivalent of such stated means em.-

pki'yed. r therefore particularly point out and distinctl claim as my invention: 1. illuminating device of the characte described, comprisin a lass tube, a metallic electrode suppo within said tube in spaced relation to the surrounding wall thereof, and a sheath of dielectric material sur- 12 thereof to remain of substan the de-.

rounding and extending from said electrode and having a conical cavity almost closed at .its free end, to confine the metal sputtered and havm a conical cavity almost closed at its free en by an inversely coned flange.

3. An illuminating device of the character described, comprising a glass tube, a metallic electrode supported within said tube in spaced relation. to the surrounding wall thereof, and 'a sheath of dielectric material surrounding and extending from said electrode and having its inner surface presenting a conical contour narrowly diverging from the electrode and then converging by successive truncated cone faces.

4. An illuminating device of; the character described comprising a glass tube, a metallic electrode supported within said tube in spaced relation to the surrounding wall there- .of, and a sheath of dielectric material surrounding and extending from said electrode and having its inner surface presenting a conical contour narrowly diverging from the electrode and then converging by a shar ly inturned truncated cone face with a ess sharply inturned truncated cone face extension.

5. An electrode element for an illuminating device of the character described, comrising a member of dielectric material havmg its inner face coated with metal and presenting a conical cavity almost closed at its free end to'confin'e themetal sputtered within the same. A 6.. An electrode element for an illuminatmg device of the character described, comprisrng a member of dielectric material having ts inner face coated with metal and presentmg a conical cavit almost closed at its free end b an inverse y coned flange. 7. e ectrode element for an illuminatmg device of the character described, compr1s1 ng a member of dielectric material havmg its inner surface coated with metal and resenting a conical contour narrowly divergmg from its inner end andthen converging by successive truncated cone faces.

8. An electrode element for an illuminatpresenting cenical contour narrowly diverging mats nner end and then converging by a sharply. .inturned' truncated cone face .witha less she; I i t ed t cated cone face ext'ensioii: y n um run Signed by me this 13th day of March, 1929.

. HAROLD HOWARD. 

